Screen, Fresnel lens sheet used for the same, and image display apparatus using the same

Abstract

The present invention provides a screen suitable for reducing the longitudinal dimension of a set. The present invention includes two prism sections. One is a totally reflective prism section (10) provided at the image generation source side of a Fresnel lens sheet (6). The other is a refractive prism section (11) provided at the image-watching side of the Fresnel lens sheet. The refractive prism section (11) includes a refractive face (e) for refracting incident light and making the light exit toward the image-watching side, a plane (f) approximately parallel to the principal plane of the Fresnel lens sheet, and a connection face (g) for continuously forming the face (e) and the plane (f).

Description

CLAIM OF PRIORITY [0001] The present application claims priority from Japanese application serial no. JP2004-166549, filed on Jun. 4, 2004, the content of which is hereby incorporated by reference into this application. BACKGROUND OF THE INVENTION [0002] (1) Field of the Invention [0003] The present invention relates to an image display apparatus for enlarging the image generated by an image generation source, and displaying the image in a projection format on a transmissive screen. The invention also relates to the screen and Fresnel lens sheet used for the image display apparatus. [0004] (2) Description of the Related Art [0005] A projection type of image display apparatus (hereinafter, called the set in some cases) projects, in enlarged form onto a transmissive screen via a projection lens and / or the like, the image displayed by the projection cathode-ray tube or liquid-crystal display apparatus (or the like) that functions as a compact image generation source, and thus forms tha...

AI Technical Summary

Benefits of technology

The present invention provides a technology for reducing the depth of an image display apparatus while maintaining high-quality images. This is achieved by using a special arrangement of prisms on the Fresnel lens sheet, including refractive and totally reflective prisms, to reduce reflection loss and improve utilization efficiency of the light. The refractive prisms have a first face that inclines to the central side of the Fresnel lens sheet, a second face that is parallel to the principal plane of the Fresnel lens sheet, and a third face that is perpendicular to the principal plane of the Fresnel lens sheet. The total thickness of the set is reduced by reducing the projection distance of the projection lens and shifting the optical-axis center of the projection lens downward. The invention also addresses the issue of discontinuity of light and suppresses the discontinuity of the light at the interface between the refractive and totally reflective prisms. Overall, the invention provides a solution for achieving high-quality images in a thin-down image display apparatus.

Problems solved by technology

Further thinning-down of the set abruptly increases the loss and the upper left and right ends of the screen decrease in brightness.

In the configuration described in Patent Document 1, however, since the configuration has refractive prisms on the light entrance surface of the Fresnel lens sheet, efficiency decreases and particularly a medium-band image (on the screen, a donut-like range) important for obtaining high image quality becomes dark.

If the discontinuity of light actually occurs, the image when viewed from the front will include discontinuous sections and image quality will deteriorate.

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